False friends (valse vrienden) are words that look or sound like words in your native language but mean something different in Dutch. For English speakers, Dutch false friends include: slim (smart/clever — not slim/thin), bad (bath — not bad/evil), room (cream — not a room), kind (child — not kind/nice), man (man/husband), lamp (lamp — same!), blank (white/pale — not blank), angel (angel — same!), arm (poor — not just arm), dom (stupid — not domestic).
More Dutch false friends: eventueel (possibly, if the case — not eventually), actueel (current/topical — not actual), sympathiek (likeable/nice — not sympathetic in English sense), confident does not exist in Dutch (zelfverzekerd), brutaal (cheeky/insolent — not brutal). For German speakers learning Dutch: ook (also — same as German auch), but bald means bold/bald in Dutch while German bald means soon.
The antidote to false friends is massive exposure to Dutch in context — you see the word used in a sentence and learn what it actually means, overwriting any false-friend association. Actively keeping a false-friends list accelerates this: when you catch yourself using a false friend incorrectly (or being confused by one), add it to your list with the correct Dutch word. This conscious noting makes the correct meaning stick faster.